Flood light



Aug. 14, 1928 1,681,153

H. L.- JOHNSTON FLOODLIGHT Filed Dec. 13, 1925 2 Sheets-Sheet 1 WITNESSES INVENTOR ATTORNEY Aug. 14, 1928.

H. L. JOHNSTON FLOODLIGHT Filed Dec. 15, 1923 2 Sheets-Sheet 2 F ye.

XVITNESS 'ATTbRNEY Patented Aug. 14, 1928.

umreoy STATES nowARD .roi rnsron or ronEs'i'fHILLs, rnnnsYLvAnIA, IASSIGNOR TO wEsTmG- HOUSE ELECTRIC a MANUFACTURING COMPANY, a conroRA'rroN or PENNSYL- I VANIA. v

PATENT or1=fica "i I rLoon LIGHT. a

Application filed Deceniber 13, 1923. Serial no. 680,395.

My invention refers to lighting fixtures, particularly to floodlights which have completely closed cases] a v Hithertdfixturesof this nature have been ventilated by v a communication to the outside which permitted the escape of heated air.

The result was that dust andmoisture entered the case and became deposited upon the reflector, thus decreasing the amount of light reflected. Floodlights of certain other types had completely closed. casesbut they utilized lampsof relatively low candle power in which only a small amount of heat was generated.

The casing was so large,,.ini comparison with the lamp, that it was possible to eliminate the heat generated without special means of ventilation; r A v The increase in candle power required in a floodlight has resulted in an increasein the heat generated in the casing; Ingorder to eliminate thisheat, extra cooling means are required. Furthern'iore, floodlight apparatus is sometimes used in places where'the atmosphere is dusty and damp. 'VSuch places are often'so nearly inaccessible that proper attention cannot be given'to the floodlight. 1 The result of this condition is particularly detri mental to theeificiencyot the fixture In order to avoid this difiiculty, I provideafloodlight which is completely closed andis-sealed In such closed floodlights of high candle power,more heat, isdeveloped than can be eliminated through a case of usual construction. Therefore, in orderto distribute the 'heatthrough the reflector case and to provide adequate heat-transmitting surfaces and an adequate transmission rate, I provide a structure whereby a current of heated air is circu- .lated within the case and remote from the lamp. 7

One object of my invention is, therefore, to provide a means for distributing the heat and preventing the concentration thereof.

Another object of my invention is to pro vide means for obtaining a high rate of heat transmission through the case.

Another object of my invention is to pro vide a large area of cooling surface.

Still another object of my invention is to provide means for circulating the air in a completely closed case.

My invention is, therefore, directed to a construct on providing a means for ventilat mg the floodlight case in order to distribute the heat evolved from the lampandi to P1385 vent the concentration of the heaton the lens and thereflector. V

Specifically, I 'providea I series of. communicating ducts or passages whereby theair may be circulated from the front to the back of the floodlight case.- By reason of this con struction, I distribute the heat and prevent the concentration thereof on the lensa'nd, at the same time, set up a current of air which increases the rate'of' heat transmission and dissipation; a, i I 1 In the drawing constituting a part hereof, Figure Us a sideviewi of myfloodlight, part ly in elevation and partly in section, and 7 i Fig. 2 isa front elevational view with parts of the doorcut away. I i j The floodlight comprises a lampuland are flector easeQ. v The reflectorease has only two I openings,.oneof which is, closed by a sealed door 3 and the other of which is closed by a bolted-011 fitting l whichsupports the focusing device 5 and the lamp 1. 1, Y

The ,door 3, is provided with a floating hinge and'a lock tomaintain it in its closed position. Between the edge of the case and the door is a flexibleigasketfi which cooperates with the floating hingeand insures a moisture-and-dust proof joint; A lens 7 is mounted in the door and is provided with a similar moisture-and-dust-proof joint, The fitting 4 closing the top of the case is provided centrally with a bushing 8 through which conductor wires extend. The-bushing is so 'mounted. as to prevent admission of air. On

the brackets 10 by means of screws 12 and the outer edge of the rim of the reflector 11 bears evenly against the casing at all points except where air passages are provided.

Two openings are shown for providing communication between the chambers in the front and the back of the reflector although other passages may be provided by making openings in the reflector between any of the brackets 10. One of the passages 1a is provided by cutting away the reflector around the lamp socket. The passage 1% is shown at the top but, if need be, passages may be provided at other points by cutting away the reflector in a similar manner.

At another point. 1 provide a passage 13 around the edge of the reflector. The passage 13 is formed by enlarging that portion of the casing 2, preferably at a point diametrically opposite the passage 14 and providing a channel in the casing having walls 15.

hen the lamp is lighted, an intense heat is generated which causes the displacement of the air around the lamp. By reason of the passages 13 and 14, a differential pressure is set up which causes a current of air to circulate across the face of the reflector and the lens, around the edge of the reflector to the back of the case as illustrated by arrows 16. By reason of, the recirculation of air to and from the lamp chamber, a convection current or turbulence, illustrated by arrows 17, is induced in the lamp chamber next to the lens. The air that is circulated in the lamp chamber is cooled by its Contact with the lens. However, a considerable amount of the cooling is accomplished in the chambers between the reflector l1 and easing 2, as iron is a more eflicient medium of heat transmission than is a lens material. such as glass. The cooled air in the back of the case continually flows to the front of the case where it, in turn, becomes heated. The movement of the air accom plishes two results. First, the heat generated in the lamp is dissipated and carried to a remote part of the case by convection currents. Second, the heated air in passing along the walls of the case, transmits heat to the case faster than still air. The result is that a larger cooling surface is provided and, at the same time, a higher rate of heat transmission is obtained.

It will be noted that I have provided a fioodlight case in which there is no connnunication of air from the outside to the inside of the case. The case is provided with ducts or passages which direct the heated air from the light chamber around the edge of the reflector to the rear wall of the case and finally returns the cooled air to the light chamber.

Although I have described a specific e1nhodiment of my invention, 1 do not limit it thereto, since various modifications thereof will suggest themselves to those skilled in the art, without departing from the spirit of my invention, the scope 01 which is delined by the annexed claims.

I claim as my invention:

1. A lighting unit comprising a closed casing, a lamp mounted in said casing, a reflector, means for mounting said reflector in said casing for providing a lamp chamber and a cooling chamber, means in said reflector for providing a passage between said chambers and an outwardly curved portion in said casing provided with inner upstruck portions for providing a channeled passage between said chambers.

2. A. floodlight comprising a closed casing, an air-and-dust proof door thereon, a lens in said door, an externally operated focusing means in said casing, an air-and-dust-proot electrical connection, a reflector disposed relative to said casing to provide a light chamber, means for circulating the air through the light chan'lber, a duct for circulating and cooling the heated air and means for returning the cooled air to said chamber.

In testimony whereof, I have hereunto subscribed my name this 7th day of December,

HOWARD L. JOHNSTON. 

